Don't inherit from `PhaseSettings` when not needed
Don't inherit from `PhaseSettings` when not needed

The `PhaseSettings` class only contains an `__init__` and `__str__` method. If the
`__init__` method is overriden by the subclass, there's no real point of subclassing.
This commits changes those classes to inherit from `object` instead. This creates
and easier to understand system.

Change-Id: Ia34a9e21e3f03671ba51ce503d7afb57bc194c02
Reviewed-on: http://review.couchbase.org/52371
Tested-by: buildbot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Dave Rigby <a09264da4832c7ff1d3bf1608a19f4b870f93750@couchbase.com>

dkao-cb/perfrunner,couchbase/perfrunner,pavel-paulau/perfrunner,EricACooper/perfrunner,couchbase/perfrunner,thomas-couchbase/perfrunner,EricACooper/perfrunner,pavel-paulau/perfrunner,vmx/perfrunner,EricACooper/perfrunner,mikewied/perfrunner,pavel-paulau/perfrunner,EricACooper/perfrunner,dkao-cb/perfrunner,pavel-paulau/perfrunner,pavel-paulau/perfrunner,couchbase/perfrunner,thomas-couchbase/perfrunner,couchbase/perfrunner,mikewied/perfrunner,couchbase/perfrunner,couchbase/perfrunner,vmx/perfrunner